function name(node) {
    if(!root) return root; // 注意
    return isSame(node.left, node.right)
}


function isSame(left, right) {
    if (left === null && right === null) return true;
    if (left === null || right === null) return false;
    return left.val === right.val && isSame(left.left, right.right) && isSame(left.right, right.left)
}